The Department of Foreign Affairs has confirmed that two further fake Irish passports were used by suspects in the killing of a Hamas official in Dubai.
The Department is currently trying to contact the individuals concerned.
The latest development brings to five the number of fake Irish passports allegedly used in the incident.
Earlier, the Israeli ambassador to Ireland has said he had no knowledge of the use of genuine Irish passport numbers on fake passports seized in Dubai.
Zion Evrony released a short statement following his meeting at the Department of Foreign Affairs this morning.
Hamas official Mahmoud al-Mabhouh was killed while staying in a luxury hotel in the Emirate by a group of assassins travelling on EU passports, including Irish and British passports.
The chief of police in Dubai said he is 99% sure that Israel was responsible for last month's assassination of a leading Hamas official.
Police chief Dahi Khalfan Tamim told The National newspaper that their 'investigations reveal that Mossad is involved in the murder of (Mahmoud) al-Mabhouh. It is 99%, if not 100%, that Mossad is standing behind the murder'.
This morning, the Minister for Foreign Affairs Micheál Martin said that the incident was very serious and had put the security of Irish citizens at risk.
Speaking on RTÉ's Morning Ireland, Mr Martin said he did not know whether the Israeli secret service, Mossad, had been involved, but he had serious concerns about the issue.
The three people initially identified as those whose passport numbers were used have been notified.
Two of the people, both of whom live in Ireland, were shocked to learn that their passport numbers had been used, a Department spokesperson said.
Mr Martin said the numbers were stolen but the names and photographs do not correspond.
He said it appeared that the numbers were randomly stolen from older, pre-2005 passports.
Passports in the names of six British citizens were among 11 EU identity papers revealed by Dubai police who were hunting the hit squad, which allegedly killed Mahmoud al-Mabhouh.
Former Liberal Democrat leader Menzies Campbell said Israeli involvement would be 'a serious violation of trust between nations'.
He added: 'Given the current speculation, the Israeli government has some explaining to do and the ambassador should be summoned to the Foreign Office to do so in double-quick time.'